I. Field of the Invention
The present invention relates to a wedge-type expansion assembly particularly adapted for expanding brake shoes of brake assemblies in motor vehicles.
II. Description of the Prior Arts
German Pat. No. 23 56 075 shows a prior wedge expansion device of the general type to which the present invention relates. In accordance with this prior known arrangement, the two ends of the rollers are provided with a guide pilot projecting axially over the face of the roller, each pilot portion engaging in an opening passing axially through the appropriate side portion of the roller cage. This prior known device has several disadvantages and drawbacks. For example, since the guide end of the rollers only have a small radial guide surface in the opening of the roller cage, there is the possibility of damage in operation under heavy load as a result of frictional wear. Rollers having guide pilot portions are also difficult to manufacture since the guide pilot portions must be machined concentric with the surface of the roller. It has been found that in hardening these rollers, residual stresses and quenching cracks may be formed at the transition of the face of the roller and the guide pilot portion.